This invention relates generally to precast concrete blocks and matrices or mats thereof used for the formation of revetments for holding soil in place and preventing the erosion thereof by water movement. Typically application of such mats or revetments are along steeply inclined canal or stream banks, along beach seawalls and along highway overpass embankments and the like. Similarly, the bottom of canal locks for the passage of vessels or steeply inclined drainage ditches or the like are also susceptible of soil erosion by the rapid movement of water across them.
The use of soil erosion prevention blocks and other revetment structures are known in the art. Typically a geo-textile comprising a highly porous and permeable heavy duty cloth mat is laid in place over the area to be protected. This geo-textile is then weighted down by heavy blocks of concrete or the like or by interconnected matrices of such heavy blocks. In the known prior art to the applicant the weight of such blocks and the geo-textile used in conjunction therewith prevent surface movement of the soil below the geo-textile. Pertinent prior art patents include U.S. Pat. No. 4,227,829 to Landry which discloses the use of a matrix of blocks, cable interconnected, in transverse and longitudinal directions and shaped to form an interlocking arrangement when placed together. U.S. Pat. No. 4,370,075 to Scales shows weighting blocks which are shaped to form an interlocked grid in one horizontal dimension while being cable interlocked in the second horizontal dimension. Both of these blocks have cable passage holes passing horizontally therethrough although the Scales blocks appear to have these only in one direction. Other U.S. patents showing features related to this use of weighting blocks are: U.S. Pat. No. 4,564,311 to Scales; U.S. Pat. No. 991,041 to Toennes; U.S. Pat. No. 5,087,150 to McCreary; U.S. Pat. No. 5,020,938 to Scales; U.S. Pat. No. 4,875,803 to Scales; U.S. Pat. No. 4,781,492 to Shined; U.S. Pat. No. 4,683,156 to Waters; U.S. Pat. No. 4,465,398 to Knudsen; U.S. Pat. No. 4,436,447 to Crowe and U.S. Pat. No. 4,375,928 to Crow et al. These patents are cited as being of interest but merely cumulative examples of different features of such blocks and systems thereof. For example some of these blocks may be interconnected by cables while some are held in place by vertical pilings driven through vertical holes in the blocks. While some of the blocks disclose complex three dimensional shapes to allow relative movement to each other vertically when arranged in a horizontal matrix, others have complex three dimensional shapes to allow growth of plants through them when in place or to allow sand or soil to be placed therebetween.
A common problem in all such block weighting systems is to provide a simple geometrical shape which may be economically formed by precast blocks. Similarly, it is desirable to be able to prefabricate matrices or mats of such blocks which may be strung together at a factory assembly point and handled together for shipping and laying in place rather than to have to lay in place individually at the usage site.